To date, quantitative assessments of the evolution of national rules have only rarely been conducted, leaving many questions ill-understood and unaddressed, particularly as to the features of rule stock evolution patterns. Can such patterns be traced, and if so, can the underlying causal mechanisms be identified? This article will address these questions. The premise is that forces endogenous to the rule system, inherent to any population of national rules, together with the demographic characteristics of rule makers, and the institutional features of the rule-making bodies jointly determine the birth rates of national rules. Given this key assumption, we offer a three-fold contribution. First, we develop a theoretical framework that integrates ecological with demographic and institutional theories of the evolution of law. Second, we describe longitudinal quantitative data concerning rule (birth) events within the domain of postwar Dutch higher education legislation. Third, we apply negative binomial regression techniques in order to estimate a comprehensive theory-driven model specification of the underlying drivers of national rule birth.